1. Field of the Invention
The invention relates to an electrical connection device for high density contacts.
2. Description of the Prior Art
A significant example of high density electric connection of contacts will be seen in reference to the substrates which form supports for integrated circuit devices The face of the substrates which carry the integrated circuit devices include a network of interconnection conductors for these devices and areas of peripheral contact constituting the input and output poles of the substrate. The substrates themselves may be mounted on printed circuit cards provided for their electric interconnection and provided in consequence with contact points destined to cooperate with the respective areas of the substrates, through electric connection devices.
For a classic substrate of square form having for example 46 contact areas on a side with a spacing of about 1 mm and a width of about 0.6 mm, the connection of the contact areas on a side of the substrate to the corresponding contact points or pads of a printed circuit card is made by means of a device put in place beginning with a comb composed of equidistant parallel spikes corresponding to the spacing of the areas and of the contact points or pads. On the side of the substrate, the combs form a clamp clamping the corresponding side of the substrate while making contact, by soldering, with the areas disposed on this side. On the card, the other extremities of the combs are soldered to the contact points or pads, the combs being maintained equidistant by means of an insulating bar or an insulating link. This connection device has the advantage of being flexible, operable and removable, features which are particularly important for this type of connection as will appear from the following.
As integrated circuit devices become more and more dense, for the best benefit of the advantages of large scale integration (LSI) and of the miniaturization resulting from the integrated circuit devices, the conductors of the interconnection network and the areas of contact that comprise a substrate become more and more dense. By way of example, the actual substrates in question are square plates of about 80 mm on a side, comprising 150 contact areas on each side with a spacing of about 0.5 mm and a width of about 0.3 mm. Present electric connection devices available do not assure an electrical and mechanical connection which is dependable, easily removable, relatively flexible and easily reproducible in large numbers. The detachability of connection devices is an essential factor when taking into account the high price of a substrate equipped with a large number of integrated circuit devices. However, the replacement of a failed substrate on a printed circuit card for repair and future reuse should not alter the quality and the reliability of the connection to the areas and contact points, both from the electrical and mechanical points of view. The fineness of the contacts and of the contact points due to the high density of connections and the particularly close spacing in the case of the substrates makes it extremely difficult to successfully detach such devices, particularly if they are fixed by solder. Thus, principally in the area of maintenance, the facility of the spacing of the connection device and its replacement are important considerations and, if possible, replacement should be done without the intervention of costly or encumbering material or apparatus.
Finally, flexibility of the connection device is necessary for the following principal reasons. On the one hand, the substrates are not always flat. For example, the several bakings that they undergo for solidification of the insulating and conductive layers of the interconnection network deposited by serigraphie are susceptible to alter more or less, locally or entirely, their initial flatness. On the other hand, the printed circuit cards are, of large surface since they are conceived to support up to a dozen substrates, and a relative flexibility. Further, the areas of the substrates and the contact points of the cards are not always of regular thickness. Under these conditions, it is necessary that the connection device be sufficiently flexible to establish an efficient connection in spite of the deformations in the substrate surface and of the cards and light variations of dimensions between areas and between contact points which come within the zone of predetermined accepted tolerance.